In a case of electric appliance requiring a high output, its total output is limited according to standards and power safety. That is, the total output of the electric appliance in a home power may be within an allowable current corresponding to standards of a power.
For this, after the power type is determined by detecting the connection state of a power cord of a product, the total load of electronic appliance, and the total output for the total load are limited according to standards corresponding to the power types. That is, a total current amount is limited.
More specifically, the power types may be single-phase, two-phase, and three-phase. In the two-phase, only two-phase is used in a power of the three-phase. This concept will be applied to this present invention. When the power types are different, an allowable current amount is set by standards of a power. For example, when a power cord of a product is single-phase or three-phase, an allowable current is relatively large 40 A, and when a power cord of a product is two-phase, an allowable current is 16 A. Therefore, a corresponding output needs to be within an allowable current.
Hereinafter, a heater for cooking appliance will be used as an example to illustrate a related art device for limiting a current.
The related art device for limiting a current includes a power detecting unit sensing input a power type (i.e., single-phase, two-phase, or three-phase) connected to a power cord, a relay connected to the heater in a one-to-one correspondence to switch a corresponding heater, and a micom controlling on/off of the relay to selectively operate the heater according to a power type detected in the power detecting unit.
Further more, although the power cord is two-phase, the micom limits the operation of the heater for safety of an input power and electric appliance when a user operates the heater to exceed a total allowable current amount and also operational conditions are inputted to exceed a total allowable current amount. The micom limits the operation of the heater in an aspect of software.
However, when only the micom limits a total output according to standards of a power, a current suddenly may exceed an allowable current in a case of micom malfunction. Therefore, a circuit breaker is turned on or a fire due to a power cord overheating occurs. That is, safety accident may occur. Since there is no preparation for a micom malfunction, safety and reliability of a system deteriorate.